The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
The present disclosure will be described below primarily in connection with loads in an on-board electrical system in motor vehicles. However, it is understood that the present disclosure may be implemented in any application in which electrical connections are to be protected.
Melting fuses are generally used in motor vehicles to safeguard electric lines against overloads. In particular, melting fuses are known for this in which a gap between two printed conductors is bridged with the aid of a melted metal body such as one of tin. Such a fuse arrangement is disclosed in DE 10 2014 115 588, for example.
As an alternative, electronic circuit breakers are used that are configured to be triggered when a safeguarding condition is met. The safeguarding condition may depend on the signal on the line to be protected or on another event, with the result that an overload situation or damage to a load is prevented. One example of a safeguarding condition is that the signal reaches or exceeds a predetermined threshold value (or drops below this threshold value). In this manner, an unsafe increase in current (or voltage or temperature) can be recognized and the safeguarding event triggered.
An intelligent on-board electrical system with power distributors must carry out two fundamental tasks: first, to supply and cut off the consumer via a circuit element on the high-voltage side (high side), and second, to protect the consumer from gradual overcurrents and hard short circuits. To provide protection from hard short circuits it is necessary to measure the current. Conventional methods are based on a shunt-current measurement using special integrated circuits. Many integrated modules such as LINEAR TECHNOLOGY (LT) 6108 or INA200 (i.e., a shunt monitor by TEXAS INSTRUMENTS) are available for this on the market. Unfortunately, for more accurate current measurement this method is usually associated with relatively high costs, required supply voltages and with relatively high current consumption in the ON state.
The German patent application publication DE 10 2011 121 850 A1 describes a circuit breaker with a switching unit configured to interrupt a circuit; a sensor unit configured to determine the value of a variable that is characteristic of a current flowing in the circuit; and a control unit configured to control the switching unit as a function of the determined value so as to interrupt the circuit; and a self-preservation circuit configured to maintain a switched state of the switching unit after the circuit is interrupted by the switching unit, until such time as a signal from the control unit activates the switching unit to cancel the circuit interruption.
United States patent publication US 2005/0135034 A1 describes a resettable circuit breaker comprising a current monitoring and interrupting circuit with an electrically conductive line that conveys a current. A sensor emits a voltage level as an indication of the magnitude of the current. A comparator compares the voltage level to a reference potential and generates a circuit indication signal. A logic-based interrupter controls the current in the line as a reaction to the circuit indication signal.
United States patent publication U.S. Pat. No. 6,594,129 B1 discloses a semiconductor relay system to supply a lamp load under ON/OFF control by a microcomputer, using a semiconductor relay.
The German patent application publication DE 10 2011 057 002 A1 shows a device for monitoring the operating state of a reverse polarity protection device provided between a voltage source and a load and having a metal-oxide-semiconductor field-effect transistor (MOSFET) switching unit that is capable of being controlled as a reaction to a gate-triggering signal from control means into an ON state of its channel. It is provided therein that means of detecting a voltage drop across the channel are associated with the MOSFET switching unit and that they are configured in such a way that in the event of an unreversed polarity of the voltage source the detection means generate a detection signal corresponding to an activation state of the MOSFET switching unit.
An electronic circuit breaker may have the drawback that it reactivates the line being monitored as soon as the safeguarding condition is no longer met. Another disadvantage may be that the electronic circuit breaker, like an electrical fuse, cannot be reset. Yet another disadvantage is a relatively high quiescent current consumption.